Stabilizer for inhibiting sucker rod buckling during compression moments in artificial lift wells

ABSTRACT

A helical solid profile attached and originating from the outer diameter of a composite or steel sucker rod and extending approximately to the inner diameter of the production tubing, running axially along the sucker rod body and affixed to it for reinforcement and stabilization of the sucker rod tension member body in axial alignment to the central axis of the production tubing which the sucker rod member is housed in, whereas the helical solid profile is made of material which is for acceptable use within the production system environment, the helical solid profile purpose being to control and reduce the sucker rod&#39;s deflection during compressive moments, extending the life of the sucker rod or reduction in stress and erratic buckling cycles.

TECHNICAL FIELD OF THE INVENTION

The present invention relates in general to sucker rods for down-holewell pumps, artificially lifting fluid from wells, and in particular tosucker rod guides and centralizers which prevent sucker rod buckling,bending moments and premature failure at the ends of mold-oncentralizers, and premature sucker rod failure.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part application of: andclaims priority to, U.S. Provisional Patent Application Ser. No.62/848,189, filed May 15, 2019, invented by Jonathan R. Martin, andentitled “Stabilization Tool For Use In Inhibiting Sucker Rod BucklingDuring Compression Moments In Artificial Lift Wells.”

BACKGROUND OF THE INVENTION

Sucker rods, utilized in pumping oil wells, have had little innovationover the last 75 years. The majority of sucker rods are made from steel,with some formed of composite materials. Steel sucker rods have upsetsforged on the ends which are machined to shape and to create threads forco-joining multiple sucker rods at well installation by use ofinternally threaded sucker rod couplings. Sucker rods connect thesurface pumping unit which moves up and down, to the down-hole pump,which also moves up and down. The sucker rods are contained inside theproduction tubing, which the production fluid, predominately a mixtureof oil and water, flows up through on its way to the surface. Suckerrods are also used in progressive cavity pumping systems as a rotatingshaft from the surface to the down-hole progressive cavity pump. Suckerrods are expected to be lifted by the surface pumping unit, lifting theweight of the rods and the weight of the fluid together. On thedownstroke, the rods are expected to fall through the fluid under theirown weight through the fluid and to remain in tension. Sucker rodspreferably have small tension loads on the down-stroke of the pumpingunit as they are suspended in the fluid column under gravity and theirown weight and high-tension loads on the upstroke due to lifting theweight of the rods themselves, combined with the weight of the fluidcolumn as fluid is lifted to the surface.

During use, sucker rods are cycled upward and downward within productiontubing to pull fluids from within wells. During the lifting part of thecyclical motion, sucker rods are exposed to peak lifting loads comprisedof: the weight of the sucker rod string at a point on the sucker rodbeing evaluated, the summation of the sucker rod string buoyant weightbelow it, the total weight of the fluid column which acts on the plungersurface area of the downhole pump, inertia loads from the decelerationof the sucker rod string as it reverses direction from a downward motionto an upward motion during the cycle of the pumping unit, and anyfriction or drag loads where the tubing wants to oppose or restrict themotion of the sucker rod string moving in the upward direction. In thelowering of the sucker rod string during half of the cycle of thesurface pumping unit, the sucker rods are intended to stay in tensionthrough gravity loads. The load applied to a sucker rod in the downwardmotion is comprised of: the weight of the sucker rod string at a pointon the sucker rod being evaluated and the summation of the sucker rodstring buoyant weight below it, inertia loads from the deceleration ofthe sucker rod string as it reverses direction from an upward motion toa downward portion of the cycle of the pumping unit, and the summationof any friction or drag loads where the tubing wants to oppose themotion of the sucker rod string moving in the downward direction. Duringthe release of the fluid load at the peak of the sucker rod stringmotion, there is an inertia effect on the sucker rod string whichapplies negative loading on the sucker rods resulting in a ‘neutralpoint’ in the sucker rod string. This neutral point location is found bysolving for the inertia-based negative loading being equal to thelocation in the rod string where the buoyant weight and gravity load ofthe sucker rod string are equal. At the neutral point and below to thedown-hole pump, the sucker rod string transitions into compressionrather than remaining in tension.

Other well dynamics, such as intended pump tagging (the down-hole pumpfinds bottom and is ‘stroked-in’ before the sucker rod string achievespeak bottom of the downward motion in the cyclical motion), inertiastrain from the deceleration of the sucker rod string as it reversesdirection from a down-ward motion to an upward motion, stuck pumps fromtrash, deviation, among other things, can also induce compression loadsinto the sucker rod string much further up the sucker rod stringassembly. At the workover rig during system assembly of the sucker rodsand the down-hole pump within the well, the rig operator willmomentarily lower the rods through the tubing to apply a significantload on the down-hole pump, attached to the lowest sucker rod,stabilizer bar (short length, large diameter rods with sucker rodcentralizers), or sinker bar (heavy, large diameter sucker rods) so thedown-hole pump can be ‘seated’ in the seating nipple at the bottom ofthe well, locking the down-hole pump in place during operation of thewell. This is pure compressive loading on the down-hole pump through therod string, which makes the rods buckle within the tubing atinstallation. Compression within the rod string is inevitable andsometimes applied intentionally, potentially leading to micro-cracks inthe surface of the steel sucker rod body for propagation and pre-maturefailure. Compressive loads applied to sucker rods with centralizers leadto an increase in stress at the edges of the centralizer, sometimesbeyond the yield strength of the sucker rod. This, applied in cyclicalpatterns, will inevitably lead to microcracks in the surface of thesucker rod, further propagating and leading to sucker rod failure. Pumptagging also occurs. Pump “tagging” is purposefully bottoming out thepump and inducing compression on the rod string, which is a commonindustry practice. The industry has a phrase, “If it ain't bumpin', itain't pumpin'.” This phrase relates to tagging the pump, which hasbenefits for pump performance but is detrimental to the sucker rodstring. Regardless of best pumping practices in application of beam-liftproduction wells, nature and the chaotic, uncontrollable nature ofsolids (sand, typically) flowing into the down-hole pump, in addition tointermittent trapped gas or lack of fluid intake, all lead collectivelyto guaranteed compressive stress in the rod string.

Through deep, deviated or horizontal well-bores, tubing is not straightand therefore the rod string travels through twists, bends, and turns(deviation from vertical) which often creates compression moments duringthe actuation of the sucker rods. Other drivers of compressive momentson the sucker rod string come from gas or fluid pounding, pump tagging(the down-hole pump finds bottom and is ‘stroked-in’ before the suckerrod string achieves peak bottom of the downward motion in the sinusoidalmotion), slug flow (chaotic gas/liquid fluid intake at the pump), pumpfriction, or cycling the pumping unit too quickly, among other reasons.These compressive moments on long slender columns, the sucker rods, makethe sucker rod unstable and therefore the sucker rod buckles within theproduction tubing. The buckling action of the sucker rod then createsmomentary high stresses which the sucker rod was not designed for,causing damage to the sucker rods and the tubing itself. Repetitivebuckling within the well then creates sucker rod failures through cracksin the surface from repetitive high-tensile surface stress andaccelerated time to fatigue failure.

FIG. 15 is a side elevation view of a sucker rod have a central portionwhich is centered within production tubing during buckling. Bending ofthe sucker rod adjacent to the conventional centralizer, while theconventional centralizer retains the central portion in a fixed coaxialrelation with the production tubing, results in his point stressadjacent to the centralizer. Stresses are concentrated as points C1, C2.T1 and T2. T1 and T2 are shown as tensile loads and C1 and C2 arecompressive loads. The loads will be applied cyclically with each strokeof the rod pump.

During buckling or compression, once the slender column becomes unstableand buckles due to the eclipsing of Euler's critical buckling load,monumental stresses are created which can exceed the yield strength ofthe steel. This instability and stress are only present because thebuckling behavior is allowed and the sucker rod is so rigidly forced tothe center of the tubing. This happens because the four-fin design isaxially forcing alignment to the center of the tubing.

By using the helical design of a stabilizer of the present disclosure,we are only forcing the rod to the center of the tubing from onevector/direction at a time. Therefore, the rod is completelycentralized; however, it is allowed to flex as necessary if axialdeflection is required (buckling). This unique design eliminates andrelieves the typical failure mode of such rods which happens at theedges of traditional sucker rod guide due to this peak stress area.Corrosion, fluid turbulence, erosion with solids swirling on the rod,all play a part in the accelerated fatigue and failure of the sucker rodat the edge of the rod guide. The single helical fin wrap of the presentdisclosure allows for four time the fluid flow area in comparison to thetraditional four-fin design. The fluid turbulence is non-existent, againrelieving another failure mode on traditional sucker rod and four-finsucker rod guide systems.

These compressive loads and resulting bending moments are attempted tobe controlled through strategic programming and closed-loop controlsystems at the surface with the pumping unit. There has long been a needto address sucker rod string protection and address sucker rod stringcompression, bending moments, and accelerated fatigue failures along thesucker rod string. In evaluating failures of sucker rod systems fromindividual wells, industry failure analysis experts encounter hundredsof well failures every single day as a result of accelerated fatigue andbending moments at the forged upset transition and at the edges of thesucker rod centralizers or guides caused by compressive loads and theresulting buckling of the sucker rods string.

Operators, individuals, and engineers have long seen the need to helpstabilize and centralize the steel sucker rod within the steel tubing,preventing steel-on-steel rubbing, contact, and wear. In operation,sucker rods can rub against the steel tubing and wear a hole in thetubing or wear through the sucker rod itself, also leading to pre-matureproduct failure, putting the well offline and therefore no longerproducing fluids until the well has been serviced and repaired. Rodcentralizers began as steel welded paddles and scrapers for movement ofparaffin and isolation of the sucker rod from the production tubing.Molded polymer sucker rod guides and centralizers have since become thego-to solution for alleviation of this metal on metal wear, typicallycomprising of multiple vanes, 2-vanes or more (usually 4 vanes), toforce the rod centrally in the tubing. Conventional sucker rodcentralizers have evolved to thermoplastic and thermoset polymericmaterials molded to shape directly on to the sucker rod, in addition tostand-alone components which can be attached to the sucker rod in thefield. These various options provide an excellent remedy when the suckerrods are in tension and remain in tension within the well duringinstallation and operation of the well. However, compression momentsoccur in sucker rods during use in oil wells.

Sucker rods under compressive loads can buckle, creating bending momentsat the forged upset transition and at the ends of sucker rodcentralizers. The bending moments occur cyclically, accelerating suckerrod fatigue, leading to failure. The sucker rod's axial exterior surfaceduring compression while buckling contact the production tubing betweenthe sucker rod centralizers causing wear of the tubing and the suckerrods. These compressive moments also induce a negative load on thesucker rod, a long slender diametric rod, to which the sucker rod thenbuckles within the tubing. This buckling applies significant side-loadsof sucker rod into tubing, flexing the rod. The buckling action createsbending moments at rigid sections of the sucker rod, such as at theforged upset transition at the ends of the sucker rods, leading to adrastic increase in stress and acceleration of fatigue on the suckerrod. The use of traditional sucker rod guides having 2-vanes or more,generally in a longitudinal direction, radially extending from thesucker rod body to the inner surface of the production tubing,centralize the rod in the production tubing in a rigid manner, provideadditional bending moments along the rod, decreasing rod life,ultimately leading to pre-mature failure of the sucker rod.

FIG. 16 is a graph of stress versus time for a sucker rod, depictingexpected rod stress and actual compressive stress occurring atconventional rod guides. FIG. 17 is a graph of rod load exported fromfinite element analysis during the study of buckling behavior of suckerrods and the influence of stress due to the use of standard, multi-finsucker rod centralizers. The expected rod stress is shown, along withactual stress computed due to the buckling behavior between the suckerrod centralizers. This buckling behavior creates tension on one side ofthe rod, and compression on the other, as the rod flexes and bowsoutward into the tubing. The plot shown shows expected stress ifbuckling was not a factor, versus the actual tension and compressionnodal analysis at the edge of the rod guide. If the sucker rods flex andfeature a bending moment at the edge of a rod guide or forgedtransition, the computed negative stress values on the sucker rod stringare rendered inaccurate instantly so. For instance, the flexing andbending from a bending moment can increase the stress along the suckerrod body both as positive and negative stress, upwards of four times thecalculated normal stress that would occur if there was no bendingmoment.

Under compressive loads and resulting bending moments, sucker rod guidesand centralizers do more harm than good for the sucker rod itself. Therod is forced into the middle of the tubing at the centralizer or guide;however, the sucker rod buckles between the rod guides due to constraintto the middle of the tubing because of sucker rod isolation from thefour fins. This buckling action then creates extreme stresses andbending moments at the edges of the guides. Time and time again suckerrods fail at the edge of a sucker rod guide or at the start of theforged upset transition on the sucker rod because of these bendingmoments and compression.

A sucker rod may have longer life without the use of sucker rod guidesif it is experiencing regular compressive loading eclipsing the criticalbuckling load for the long slender column of a sucker rod. Verified byphysics and engineering work, if the sucker rod is experiencingcompressive loads greater than its mathematical allowance and isbuckling between guides, more rod guides are needed to prevent suckerrod buckling, or the alternative is no-rod guides which will reduce thebending moments and stress on the rod, but increase the rod-on-tubingwear. If more guides are elected to be added to sucker rods, they mustbe able to eclipse the compressive loads the sucker rod is experiencing,otherwise the additional rod guides are increasing the stress values atthe edges of the rod guides, and the rod will fail that much quicker.Electing to use less or no sucker rod guides, the steel tubing and rodhowever will experience wear due to no isolation and centralization ofthe sucker rod on the tension upstroke.

Buckling and compression both create stress concentrations from bendingmoments which lead to a failure in the rod string, typically what iscalled a ‘rod part’ in industry for steel rods. This is where the rodbreaks from accelerated fatigue due to the bending moments creatingextreme negative stress (compression) and positive stress, cyclically,between the standard upstroke tensile stress. This results in a largernegative stress ratio, which is detrimental to fatigue life. By limitingexponential increase in tension stress on the sucker rod body due tobuckling, the fatigue life of the sucker rod is instantly increased, asshown by physics and S-N Diagrams for material science. Limiting thisstress ratio is possible by isolation of the sucker rod within thetubing, preventing buckling and creating a pure, normal stress on therod, limiting its buckling deflection and drastically reducing oreliminating the erratic surface stress on the sucker rod body. This isaccomplished by way of reinforcing the sucker rod to the center of thetubing to where it is unable to buckle. This could be done by way ofadding more and more traditional centralizers to the sucker rod (not aneconomically feasible option) or by use of the invention discussedherein. Prevention of sucker rod buckling is a dramatic improvement tothe system, leading to lengthened operational life never before seen inthe industry.

Compression and buckling failures on composite sucker rods (carbon fiberor fiberglass) typically result in broomstick failures. The fibersconstrained together by use of the pultrusion resin in the composite roddesire to buckle. The resin which binds the fibers together does nothave the radial and transverse strength to keep the fibers boundtogether; therefore, the resin breaks apart, freeing the compositefibers from their containment. The fibers of the composite rod then nolonger share the loading as intended; fibers break, the failurepropagates nearly instantaneously, and the ‘broomstick’ failure results.It is literally not possible to retrieve the broken rod from within theproduction tubing during well maintenance; rather, the tubing stringmust be pulled from the well with the sucker rod system inside of it inorder to eventually get to the failure point in the system, thus addingto more time and cost for maintenance of the system. These compositesucker rod failures also can be limited by way of keeping stress normalto the cross-section of the sucker rod and eliminating the flexing andbuckling on the fiber rods, another application for the inventionherein.

SUMMARY OF THE INVENTION

A stabilizer for a sucker rod has a continuous vane with helical profilewhich is attached along a length of the sucker rod body, between forgedupsets for steel sucker rods or between end connections for compositesucker rods. The stabilizer extends from the sucker rod body to near theinner diameter surface of the production tubing. The helical profilecontinuously reinforces and stabilizes the sucker rod, constraining thecentral longitudinal axis of the sucker rods to be coaxial with thecentral axis of the production tubing. This helical profile affixed tothe sucker rod centralizes and stabilizes the sucker rod in both tensionand compression moments, preventing the buckling of the sucker rod dueto the constant reinforcement of the sucker rod. The stabilizer ispreferably corrosion resistant, strong and rigid, yet lightweight andaffordable. The stabilizer is preferably formed of thermoset plastic butmay also be formed of molded or extruded thermoplastics, aluminum, steelor brass.

The sucker rod stabilizer has a helical profile which is attached to thesucker rod, continuously reinforcing and stabilizing the rod throughouteach coil section, increasing its area-moment of inertia (“AMOI”) as anassembly. This forces the full length of the rod to stay within thecentral axis of the tubing during compressive loading. The ideal pitchof the profile is calculated by evaluating an extreme circumstance inbeam-lifted wells, the maximum compressive loading possible (the weightof the rod string above the bottom-most sucker rod). The singular vanehelically wrapping around the sucker rod allows for more efficient fluidflow patterns, reducing drag loads in comparison to standard sucker rodguides. The reduction in fluid drag through the helical efficient designallows for more efficient energy consumption for the pumping unit on thesurface, as well as reduces the chance of solid and gas erosion andcorrosion on the sucker rod body due to momentary pressure changes madeby the surface of standard sucker rod guides which can lead to aswirling effect at the edges of the sucker rod centralizer, eroding thesteel sucker rod body away over time. Additionally, the singular vane ofthe invention disclosed herein has a greatly reduced AMOI in comparisonto traditional molded centralizers, allowing for geometric flexibilityof the plastic profile which exceeds the flexibility of the sucker rodin all directions along the spine of the coil, and where the wrap aroundpad is on the helical profile, profile flexibility is approximatelyequivalent to the three-quarter inch sucker rod flexibility. Largerdiameter steel sucker rods are far more rigid than the composite coilprofile. Simulations and real-world testing has validated that theinvention herein, molded from thermoset phenolic glass and mineralfilled material features a stiffness matrix (flexural modulus of apolymer material to which it is comprised, multiplied by the AMOI of theprofile) which is one-fourth (¼) that of sucker rod guides in industry.The polymeric profile is more flexible than other common rod guides,which allows for the rod, if it does buckle or flex, to not imposeadditional stress and bending moments along the rod body like that oftraditional molded sucker rod guides. This is the core reasoning for thelack of bending moments and prolonged sucker rod fatigue life.

A manufacturing method of the present disclosure for producing coilcentralizers includes the use of thermoset molding. Thermosetmanufacturing creates dense, non-porous parts in comparison tothermoplastic molding which tends to create voids and holes inthick-walled molded sections. Thermoset manufacturing, through the useof phenolic molding compound, provides superior wear and frictionbenefits due to thermally stable high-modulus material (relativelyspeaking to its thermoplastic counterparts), and has been utilized indown-hole oil and gas applications for decades. Phenolic resins, mixedwith a variety of fillers, are often used for tribological applicationswhere friction, drag, or wear resistance is highly desired. Plasticsindustry experts commonly recommend thermosets, and typically phenolicreinforced molding compounds, for prolonged elevated temperatureapplications requiring unmatched wear resistance. The mold tools' coreand cavity components, which are designed for the constant profile andhelical pitch on the coiled stabilizers as presented herein, may bebuilt in sections.

The present disclosure also addresses the centralizing need of thesucker rod within the tubing, and allows for, validates, and addressesthe complication of the sucker rod buckling action during compressionmoments. Compressive stresses are not so problematic on the sucker rodso long as the rod does not buckle. The goal is to contain thesecompressive instances and keep the sucker rod stable so the ultimatecompressive stress remains normal to the cross-section of the rod,drastically reducing the stress-amplitude, stress cycles and chaoticstress upon sucker rod loading. In review of FIG. 13, in one pumpingcycle of the sucker rod, there are 5 instances of drastic peaks andvalleys in stress behavior, tripling the cycle count that the rod bodyitself encounters in application. Eliminating the buckling behaviorresults in lengthening the fatigue life of sucker rods, in addition togeneral sucker rod-on-tubing wear protection.

By utilizing a helical profile, full length stabilizer along the smalldiameter sucker rod body, the sucker rod is constantly reinforced fromend to end, staying in axial alignment with the production tubing. Thehelical profile can be made from any rigid, lightweight material, as onelong unit affixed to the rod or in multiple sections to achieve the samedesired effect. In production, it is advised to use a thermoplastic orthermoset polymer material, easily molded to shape and cost-effective.The difficulty in production of the helical coil is the pure lengthrequirement to properly stabilize the sucker rod to the middle of thetubing. Sucker rods vary in length from nearly twenty-five to thirtyfeet. The sucker rod stabilization tool, to be effective, must reinforcethe sucker rod so much as to increase its critical buckling load beyondthe maximum potential compressive load in well. The maximum compressiveload in application would be the weight of the sucker rods above thespecific rod in question. The lowest sucker rod in the well has the mostcompressive loading potential, due to the full weight of the rod stringabove it. The rod just below the surface of the Earth, first in the wellhas the smallest compressive loading potential as only the mass of thesurface polished rod is above it.

DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and theadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying Drawings in which FIGS. 1through 26 show various aspects for a stabilizer tool made according tothe present disclosure, as set forth below:

FIG. 1 is a partial side elevation view of a sucker rod string disposedin a tubing string with the stabilizers extending between the sucker rodstring and the tubing string;

FIG. 2 is a partial side elevation tool of a sucker rod with one of thestabilizers secured to the sucker rod;

FIG. 3 is a perspective view of one of the stabilizers;

FIG. 4 is a section view of the stabilizer tool, taken along sectionline 4-4 of FIG. 3;

FIG. 5 is a partial side elevation view of the sucker rod tool string,showing two sucker rods having a different number of stabilizers mountedthereto;

FIGS. 6-8 are perspective views of three configurations of molds forforming the stabilizers, over-molded directly onto respective suckerrods;

FIGS. 9-11 are respective side elevation views of the stabilizer toolmolds of FIGS. 6-8;

FIGS. 12 and 13 show a comparison of the free length of the sucker rodbetween stabilizers made according to the present invention and priorart centralizers when spaced apparat along the length of a sucker rod;

FIG. 14 shows the effective distance at which the end of a stabilizermade according to the presentation invention will move with the suckerrod from being centered within production tubing;

FIG. 15 is a side elevation view of a sucker rod have a central portionwhich is centered within production tubing during buckling;

FIG. 16 is a graph of stress verses time for a sucker rod, depictingexpected rod stress and actual stress occurring at conventional rodguides;

FIG. 17 is a graph of rod load, expected rod stress, tension nodebuckling and compression node buckling;

FIG. 18 is a graph of tensile modules vs. temperatures for severalcommon sucker rod materials;

FIG. 19 is a chart listing values for boundary conditions for Euler'scolumn formula for buckling for several sucker rod end constraintconditions;

FIGS. 20, 21A and 21B are flow charts depicting a manufacturing processfor making stabilizers according to the present disclosure;

FIGS. 22 and 23 are fixtures for baking and curing stabilizers whichformed of polymers which are over-molded onto such rods in the process;

FIGS. 24 and 25 are perspective views illustrating the high erodiblewear volume of the stabilizer of the present disclosure, as compared tothe erodible wear volume of conventional prior art centralizers; and

FIG. 26 is a flow chart depicting a process for engineering stabilizersaccording to the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a partial side elevation view of a sucker rod string 12disposed in a tubing string 10 with the stabilizers 20 extending betweenthe sucker rod string 12 and the tubing string 10, centering the suckerrod string 12 within the tubing string 10. A sucker rod coupling 16connects between two of the sucker rods 14. The stabilizers 20 each havea single vane 22 which helically extends around the sucker rods 14 and athickness 18. The sucker rods 14 have a centrally disposed longitudinalaxis 38 which is generally concentric with a longitudinal axis for thetubing string 10, with the stabilizers 20 centering the sucker rodstring 12 within the tubing string 10. The stabilizer 20 and thestabilizer vane 33 have a longitudinal axis 36 which is concentric withthe longitudinal axis 38 of the sucker rod 14.

FIG. 2 is a partial side elevation view of a sucker rod 14 with one ofthe stabilizers 20 secured to the sucker rod 14 and FIG. 3 is aperspective view of the stabilizer 20 without showing the sucker rod 14.The stabilizer 20 is formed on the sucker rod 14 as a single unitarymember which is over-molded onto the rod 14 and will generally not beindependent from the sucker rod 14. The stabilizer 20 has the singlevane 22 which helically extends around the sucker rod 14. The oppositeends of the stabilizer 20 are preferably formed into the shape ofsleeves and provide molded collars 24 and 26 which provide wrap-aroundpads that extend fully around, enclose, and shrink-fit around the suckerrod 14. Similarly, the collar 28 is preferably formed in the shape of asleeve located in a longitudinally intermediate portion of thestabilizer 20, and provides a wrap-around pad which extends fully aroundand encloses the sucker rod 14. The vane 22 extends around a length ofthe sucker rod 14, gripping the exterior of the sucker rod 14 to securethe stabilizer 20 to the sucker rod 14, providing full isolation fromthe tubing string. The collars 24, 26 and 28 provide a further grip ofthe stabilizer 20 to the exterior of the sucker rod 14. The vane 22 hasa pitch 32 helically extending around the sucker rod 14. The pitch isthe distance at which the vane 22 extends in the direction of thelongitudinal axis 36 and returns to the same angular position relativeto the sucker rod 14, computed by analysis of extreme reciprocating rodlift rod string application and use.

FIG. 4 is a section view of the stabilizer 20, taken along section line4-4 of FIG. 3 which is perpendicular to the longitudinal axis 36. Thevane 22 is shown to preferably have a substantially rectangularcross-sectional area with arcuately shaped radially outward and radiallyinward ends. The vane 22 is shown extending around the longitudinal axis36. The collar 28 is shown fully enclosing an internal space in which asection of the sucker rod 14 will be located. The vane 22 along thesection line 4-4 has a radial length 34 which is extends perpendicularto the longitudinal axis 36 and a thickness 18 which extendsperpendicular to the radial length 34. The terminal end of the vane 4has an outer surface 48.

FIG. 5 is a partial side elevation view of the sucker rod string 12,showing the sucker rod 14 and a sucker rod 30 having a different numberof stabilizers 20 mounted thereto. Seven of the stabilizers 20 aresecured to the sucker rod 14 and four of the stabilizers 20 are securedto the sucker rod 30. Preferably, a greater number of the stabilizers 20are secured to each of the sucker rods 14 which are located furtherdownhole where more loading from the weight of the sucker rods string islocated and buckling tendency is much higher. For sucker rods 14 locatedfurther up-hole a lower number of the stabilizers 20 per sucker rod 14may be used where loading from the sucker rod string 12 is less andbuckling tendency is lower. Further up-hole from the sucker rod 30 asmaller number of stabilizers may be used, going from four of thestabilizers 20, to three of the stabilizers 20, to two of thestabilizers 20, and then one of the stabilizers 20 per sucker rod 30.Below is a discussion regarding calculating the number of thestabilizers 20 required per sucker rods 30 to prevent buckling anddamage from bending moments caused by the weight of the sucker rodstring 12 applied cyclically during pumping.

FIGS. 6-8 are perspective views of three configurations of molds forforming the stabilizers, over molded directly onto respective suckerrods, and FIG. 9-11 are respective side elevation views of thestabilizer tool molds of FIGS. 6-8. In addition to placing a smallernumber of stabilizers 20 per sucker rods 14 in tool string positionslocated further up-hole, the lengths of the stabilizers 20 may bereduced by over-molding stabilizers 20 of smaller lengths. The moldconfigurations 40-44 shown in FIGS. 6-1 l each provide stabilizers 20 ofthe same pitch, but with different lengths. The mold cavity 46 is shownas extending through each of the mold sections 50-58, with a form whichis generally concentrically disposed with the axis 36 for the sucker rod14 and the stabilizer 20. FIGS. 8 and 11 show a mold configuration 44using each of the mold sections 50-58 for the stabilizer 20 having thelongest length. FIGS. 7 and 10 show a mold configuration 42 which is ofan intermediate length, shorter than the longer mold length of the moldconfiguration 44 of FIGS. 8 and 11, and which is provided by removingthe mold sections 52. FIGS. 6 and 9 show a mold configuration 42 whichis of a shorter length, than the intermediate mold length of FIGS. 7 and10, and shorter than the longer mold length of the mold configuration 44of FIGS. 8 and 11, and is provided by removing the mold sections 56 fromthe mold configuration 42 shown in FIGS. 7 and 10. Thus, the same moldsections 50-58 may be used to provide stabilizers 20 of three differentlengths, but having the same helical pitch 32. Preferably, the moldsections 50-58 are each formed of two halves which are fitted around asucker rod and joined, or secured, together, and then the mold sections50-58 are secured to the sucker rod in sequential alignment for theinclusion of the end-located molded collars 24 and 26.

The helical coil mold cavity 46 shall be various combinations of themold sections 50-58, making up the full helical profile to be molded,perhaps approximately forty inches in length. By removing the section52, and co-joining modular tooling section 50, 54, 56, and 58, as shownin FIGS. 7 and 10, the molded profile can be shortened for less materialusage and less cost to the customer, perhaps approximately thirty incheslong. The constant design of the helical pattern allows for thismodularity due to consistent molded section.

Further, by removal of an additional mold section 56, and co-joiningsections 50, 54 and 58, a reduced coil length can be produced furtherallowing for cost-savings in material and cost-savings to the end-user,without the need or requirement of additional tooling expense. In thepresent embodiment, the helical profile has tapered edges on the startand end of the coil for smooth fluid flow. The mold sections 50 and 58containing the end profile taper and molded collars 24 and 26 aredesirable in use for any molded profile.

FIGS. 12 and 13 show a comparison of the free length of the sucker rodbetween stabilizers made according to the present invention and priorart centralizers when spaced apart along the length of a sucker rod. Forthe same number of centralizers disposed on sucker rods of approximatelythe same length, the free distance of the sucker rod between astabilizer of the present disclosure is L1. A similar length between twoconventional centralizers shown in FIG. 13 is L2, which is longer thanL1 of FIG. 12. Additionally the bypass area for fluid flow around astabilizer of the present invention is larger than that of aconventional centralizer.

FIG. 14 shows the effective distance at which the end of a stabilizermade according to the presentation invention will move with the suckerrod from being centered within production tubing. This transition regionextends for a distance D from the end of the stabilizer to a point alongthe stabilizer at which the rod is maintained in a substantially coaxialalignment with the production tubing. The transition region in thesingle helical blade stabilizer in combination with the sucker rod whichextends a distance D provides significant compliance, or spring-likeflexibility, in centering the sucker rod as compared to conationalstabilizers. That is, in the transition region D both the stabilizer andthe sucker rod may flex to reduce stress from being concentrated in thesucker rod at the end of the stabilizer.

The transition for bending of the rod at the ends is enabled by the wraparound sleeves providing a coupling which grips the rod with a shrinkfit. Without a secure grip between the rod and the spiral-shaped, singlefin stabilizer, the bending transition D would not be provided sincethere would be significant slip between the stabilizer and the rod. Thespiral shaped fin also grip the rod along with the wrap around sleeves,but shrink fitting a fulling enclosing wrap around sleeve provides anon-slip grip as compared to shrink fitting the spiral shaped fin tofirmly affix the stabilizer to the rod

Steel sucker rod weights range from about 35 lbs. to nearly 85 lbs.,dependent on diameter. The weight of each rod can then increasedepending if it has other accessories attached to the rod. A deep rodpumped well may approach 10,000 feet of sucker rod or more and willfeature a tapered sucker rod string, the assembly of multiple suckerrods attached together through couplings end-to-end. A tapered rodstring could be similar to that which the first 2,000 feet below thesurface is 1-inch diameter sucker rods, a very common large rod in usefor wells. The next 3.000 feet of the rod string (well depth of 2,000feet to 5,000 feet) may changeover to ⅞-inch diameter sucker rods, andthe remaining 5,000 feet (well depth of 5,000 to 10,000 feet) to ¾-inchsucker rod. Twenty-five feet of length for each sucker rod, most commonin the United States, would for this example create a cumulative weightof the rod string nearing 20,000 pounds without any rod stringaccessories. Buoyant weight of this rod string, in oil/water mixture,will reduce the effective weight of the rod string based on fluiddensity and volume of product in the well. However, upon initial installof the sucker rods and utilizing the compressive force to seat the pumpin the seating nipple, the rod string is not necessarily submerged influid therefore its full weight could be imposed on the down-hole pumpfor seating. Ironically, ¾-inch sucker rods at the bottom of the wellare more prone to compressive loading due to the accumulation of weightabove them, and therefore the ¾-inch sucker rods tend to fail muchfaster. Deep well ¾-inch rod parts are very, very common in industry.

Engineering math to calculate the necessary sucker rod reinforcement tobest prevent buckling along the sucker rod is shown below:

${{{{E = {{{modulus}{of}{elasticity}({psi})} = {29,700,000}}}{I = {{{moment}{of}{inertia}( {in}^{4} )} = \frac{\pi D^{4}}{64}}}{{L = {{length}{of}{reinforcement}}},{{helical}{pitch}({inches})}}{F = {{load}({lbs})}}{n = {{{boundary}{condition}}{Euler}}}}’}s{Column}{Formula}:}{F = \frac{n\pi^{2}{EI}}{L^{2}}}$

FIG. 18 is a graph of tensile modules vs. temperatures for severalcommon sucker rod materials, and FIG. 19 is a chart listing values forboundary conditions for Euler's column formula for buckling for severalsucker rod end constraint conditions. The boundary condition can varyfrom 1 to 4, depending on the fixture reinforcement type for the suckerrod: pivot, fixed, or a combination of the two. Sucker rods areconstrained to the inner diameter of production tubing and thereforebehave somewhere between fixed and pivot connections.

The weight of the rods and peak compressive loading is known based onspecific rod-string design for the particular well. The formula shall berearranged to solve for Length, providing for the optimal length ofmoments of stabilization and reinforcement. For the product designenclosed, the helical pattern shall have a pitch no less than what isrequired of the well and loading.

Rearranged the formula and solving for Helical Pitch provides thefollowing:

${{Helical}{Pitch}} = \sqrt{\frac{n\pi^{2}{EI}}{F}}$

Peak compressive loads at various boundary conditions are shown in TABLEA:

TABLE A Rod Calculated Diameter Depth Compressive Load Helical Pitch(inches) (feet) Potential (lbs.) (inches) ¾″ 10,000 feet  ~20,000 lbs. n= 1: 15.1″, n = 2: 21.3″, n = 4: 30.2″ ⅞″ 5,000 feet ~12,000 lbs. n = 1:26.5″, n = 2: 37.5″, n = 4: 53.0″ 1″ 2,000 feet  ~5,500 lbs. n = 1:51.0″, n = 2: 72.2″, n = 4: 102″

Looking at the table above, the smallest diameter rod with a pivot end(n−1), would require approximately a 15-inch helical pitch. Sucker rodbehavior in well and co-joined with traditional sucker rods is morereflective of an n=2 scenario, where there is a fair amount of rigidityat the coupling due to the increased diameter of the steel couplingprofile. This is the most conservative pitch spacing and could beconsidered for the above to provide maximum rod stabilization; however,sucker rods are conjoined and often reflect a scenario much closer tothat of Fixed End condition (n=4). In observance of the above data, itis obvious that as load decreases and rod diameter increases, the suckerrod becomes more stable, and less likely to buckle. A 1-inch diametersucker rod with 2,000 feet of rod above it, has about 5,500 pounds ofcompressive load potential and requires reinforcement between 51 inchesand 102 inches based on the end-condition in which it is constrained. Ina well with a full fluid column, the compressive load potential reducesgreatly due to buoyancy.

In addition to the helical pitch consideration for maximum effect onstabilization of the sucker rod, a material selection for the helicalprofile shall be evaluated. In mass manufacturing, plastics dominate.Injection molding of thermoplastics for down-hole use have been aroundsince the mid-20^(th) century, particularly for the thermoplastic suckerrod guides which can be over-molded directly on the sucker rod. FIG. 14is a graph showing tensile modulus verses temperatures for severalcommon sucker rod materials.

Recent advancements made by Martin shown in U.S. Pat. No. 9,869,135,issued Jan. 16, 2018, provide for thermosets to be efficientlymanufactured directly around sucker rods for sucker rod guide use.However, U.S. Pat. No. 9,869,135 does not address the buckling nature ofsucker rods and instead it is directed toward the periodicimplementation of multi-vane centralizers around sucker rods, similar tothat of which has been done for nearly 60 years and is limited in scopedue to the prior art. If sucker rod pumping was in an ideal world andperfect state, current market offerings of multi-vane centralizersperiodically molded around the sucker rod, typically 4 to 8 guides perrod, would be a desirable and effective solution. In fact, traditionalsucker rod guides are effective regardless of which material rod guidesare comprised of. High modulus and high compressive strength materialsat the application temperature dictate the performance of the product.Because thermosets do not soften when heated like thermoplastics,thermoset performance is predictably better than thermoplastics for theapplication and use in elevated temperature, down-hole environments.

In molding and manufacturing of sucker rod guides, the molded plasticprofile is formed directly around the sucker rod. As the moldingmaterial is cooling, whether thermoset or thermoplastic, it shrinksaround the sucker rod, hugging and bonding to it tightly, creating atight friction bond between the sucker rod surface and centralizer,inducing hoop stress at the inside diameter of the molded profile. Asimilar manufacturing method can take place with the helical profile.The material shrinkage, a component and property of plastic compounds,takes place in the longitudinal and transverse direction relative to theflow of material when molding. Further, this shrinkage takes place inaccordance with the centroid of the molded part. Wrap-around pads forthe helical profile, for complete sucker rod encapsulation can be addedperiodically for further shrinkage and bonding to the sucker rod.Further, the surface roughness of the sucker rod can be modified orimproved while maintaining compliance to sucker rod manufacturingrequirements, leading to more texture for the plastic molded profile tofill in and intimately connect to.

Molding plastic components around foreign objects is referred to as“insert molding” and is common practice. All engineering plasticsuppliers recommend the heating of the insert to match the recommendedmold temperature in order to maintain ideal plastic properties. Theforce to displace a sucker rod guide axially, which is molded around asteel sucker rod, varies based on centralizer/guide selection, testingtemperature, steel rod surface finish, and molding pressures; thedisplacement value varies from 1,500 lbs.-force to 25,000 lbs.-force,strictly created from shrink fit, rod texture and friction bonding.

Specifically discussed relating to the manufacturing of thermosetphenolic resins, mold temperature and insert temperature (the suckerrod) must be strictly monitored and controlled. The chemical reactioncuring process of thermoset resins is sensitive with regard to time,temperatures, and pressures. Too cool of insert (sucker rod) or too coolof mold temperature will create parts which have not undergone acomplete chemical reaction. Any un-cured resin components in the moldedprofile, when subject to down-hole fluids, will wash out and leave voidsin the profile, most typically observed against the sucker rod body,leading to centralizers which slip, slide and move along the sucker rodbody axially. This is a result of poor manufacturing and qualitycontrol. Ideal insert molding requires the insert to match the resinsupplier and advised temperature of the mold tool, both in thermoplasticand thermoset molding. In this case for phenolic resins, the inserttemperature would approximately be between 325 degrees F. and 375degrees F. In the case of thermoplastic molding, the insert temperaturewill most likely be between 200 degrees F. and 300 degrees F.,respective of the resin manufacturer's guidelines. The surface of thesucker rod steel in injection molding is exposed to temperatures inexcess of 500-700 degrees F., caused by material melt temperatures. Thisis very important in studying and understanding consistent non-linearplastic material properties of the finished molded profile. Withoutproper curing of thermoset materials, the molded plastic parts aroundthe insert may slip, slide, or break apart due to a lack of molecularbonding and crosslinking, which does not allow for the molded part tofeature its extreme hydrocarbon resistance. Following the manufacturerguidebook is imperative to create parts which match that of thelab-molded test parts, representing physical and mechanical propertiesin the material datasheets. Failure to do so will result in subpar partswhich do not meet the application and industry requirements fordown-hole centralizer or stabilizer tool use.

FIGS. 20, 21A and 21B are flow charts depicting a manufacturing processfor making stabilizers according to the present disclosure. In theprimary manufacturing process and due to the extended length of thesucker rod stabilization tools, a sucker rod must be cleaned from itscorrosion inhibitor coating down to bare steel. Common industry practicefor a number of decades includes use of wire wheel brush systems whichremove the coating and expose bare steel for maximum consistency inmolding. Additionally, new and novel for the manufacturing of the suckerrod stabilization tools described herein, is the addition to themanufacturing process of full-length direct conduction heating of thesucker rod body prior to molding, with adjustable PID closed-looptemperature control system. This ensures the heating of the inserts isat an acceptable range complimentary to the molding process for thethermoplastic or thermoset resins, heavily advised by the materialsuppliers of all plastic resins and compounds. The conduction heatingsystem features aluminum tubing open on each side, with heating elementssecured to the outside of the diameter of the tubing. The tubing is thendirectly heated and monitored with thermocouples. The sucker rods slidein one end and direct heat conduction from the aluminum tube heats thesteel sucker rod body. The sucker rod body is heated for a given amountof time complimentary to the molding and manufacturing cycle of thesucker rod stabilizers. The sucker rod and the molded sucker rodstabilizer are then ejected through robotic automation from the otherend of the aluminum tube from which the sucker rod was initiallyinserted. The aluminum tube is aligned with the automation cells in andaround the custom-tailored hydraulic molding presses for passing thesucker rods and molded sucker rod stabilizers directly into one of thecells. Temperature controls are integrated with the parent industrialcontrol system which is monitoring and regulating both the press moldtemperatures and the oven temperatures. Any thermal parameters out ofallowance shut down the parent system, creating a proactivemanufacturing cell rather than typical human-intervened reactivemanufacturing. This ensures the plastic, as it flows from the injectionlocation through the mold cavity, does not see, recognize or behave anydifferently along the sucker rod insert than it would along the moldcavity surface. In order to flow thermoset phenolic resin along the longhelical profile, the mold temperature and insert temperature must bekept steady and complimentary to one another, low enough to allow resinflow through the cavity without chemical crosslinking and solidificationprior to the filling and packing of resin within the mold tool andaround the insert, yet high enough to encourage flow and achieve anacceptable cycle time for the curing of the phenolic resin. Thisdelicate balance is specific to the stabilization tool manufacturingprocess and requires hyper-accurate resin temperature and speed controlthroughout the flowing and filling of mold cavities.

Furthermore, upon the ejection of the molded parts, the sucker rods withthe molded stabilization tools then are loaded into a multi-row andmulti-column oven with similar aluminum tubes and heating elements tothe foregoing. This oven is affixed to a hydraulically actuated lifttable assembly which allows for vertical movement, keeping the moldedgoods in a heated environment as a post-bake, quality control process toensure no plastic molded parts leave the manufacturing facility withoutan ideal cure profile having been completed. Each row can be in axialalignment with the tracks in front of the hydraulic molding presses byway of height-regulated automation. Automated systems, after the moldingof the stabilization tools, load the molded profiles and sucker rodsinto the post-molding curing tubes. The tubes then move vertically afterevery molding cycle. Each tube is independently controlled with PIDclosed-loop temperature control system, allowing for tube specifictemperature profiles to be regulated complimentary to the moldtemperatures in the hydraulic press molding cell. As the scissor tableraises or lowers, the tubes allow for the cycling of new moldedcomponents in each row. Once each row is occupied, the scissor tableresets, the automation then loads the next freshly molded rods into thetubes which are occupied, displacing those molded sucker rods which havebeen in the oven for an extended period of time onto the de-flashing androd-coating area. The system then continues and repeats. The system isarranged so that all molded components are subject to curing temperatureor post-bake temperature 6 times longer than necessary to cure themolded profile. Industry recommended practice for a quality molded partis approximately one minute of curing time per ⅛″ of thermoset phenoliccross-section. In the case of traditional, large cross-section suckerrod guides, this would be approximately a six-minute curing cycleassuming the sucker rod inserts are heated to the same temperature asthe mold tools. In the event of a cooler rod temperature, the curingtime would need to increase. It is possible to mold parts faster thanthis timeline as the chemical reaction based molded is exothermic andthe steel rods will hold and act as a heat source to encourage phenoliccuring; however, its consistency and the molecular integrity of themolded part may suffer, and the molded profiles' material propertieswould not represent the material datasheet accurately. This would leadto an accelerated wear rate in application, or a reduction in frictionalbonding to the sucker rod insert, again leading to slipped centralizerswhich may break or de-bond from the sucker rod body.

FIGS. 22 and 23 are fixtures for baking and curing stabilizers formed ofpolymer materials which are over-molded onto sucker rods in a batchprocess. The automation system for the handling of sucker rods both fromthe feed-oven, in and out of the molding presses, and into thepost-molding baking oven is handled via precision ball-screw andbelt-drive linear slide assemblies, powered by servo-controlled motors.Servo motors with specialized encoders are used with constant positionfeedback, and the repeatability is as accurate as 1/6400^(th) of arevolution. This allows for positional accuracy through themanufacturing process nearly less than 1/10,000^(th) of an inch(0.0001″). Furthermore, the automated loading and unloading of suckerrods into the mold tools helps regulate typical human error or abusivehandling, as the automation is programmed with force, velocity andtorque control to allow for precise and gentle handling of the suckerrod in and out of the production cell. This handling system, along withthe pre- and post-bake oven system, is entirely new, unique, and novelto the manufacturing of sucker rod centralization or protection devices.With modem control closed-loop feedback and integration of one processto another throughout the facility, reduced overhead, product abuse, andhuman error in handling and processing of plastic molding and inserts isrealized throughout the facility. Industry respected care and handlingguidelines for sucker rod products are thereby forced into compliancevia automation instead of requested to be held in compliance by humanstaffing.

Although the industry prefers plastics as lightweight, known consumablesin the down-hole space for sucker rod, aluminum, brass, and steel couldalso be used to provided stabilizers for stabilizing the sucker rod incompressive moments. However, the cost, mass and material density of thestabilization member must be considered. Other variants of manufacturingcapability include radial pultrusion coiled profile, which could then betwisted onto and around the sucker rod and bonded with animmersion-service adhesive, such as various grades of epoxy ormethyl-methacrylate. Another alternative for the manufacturing of thehelical stabilization tool can be radial extrusion variants also bondedwith immersion service adhesives.

Thermoplastic straight extrusions of the continuous profile can beproduced with post processing of heating and softening the polymericmaterial, mechanically yielding the thermoplastic material to helicalform, and cooling. This manufacturing method would save on capitalequipment costs; however, the stabilization tool's wear and temperatureperformance are limited in comparison to the preferred method thermosetmolding with modular tooling.

Metallic sections could also be cast individually and bolted togetheraround the sucker rod, creating a continuous profile from end to end.

Thermoset polymeric materials are not melt-processable, do not softenwhen heated, and are ideal for use in high pressure, high temperatureapplications such as down-hole oil-wells. Their use is not new andunique to down-hole applications, being accepted for down-hole use fornearly 50 years. For sucker rod stabilizers, from a processing, cost,and ease of manufacturability for long components along a sucker rodbody, thermoset molding, particularly for glass and mineral reinforcedthermoset phenolic resins, is an ideal candidate for the stabilizationdevice. Plastic performance is stable, consistent, and notablyoutstanding as recognized by industry as long as manufacturingconsistency is upheld. Material density and cost are proven cooperativewith market requirements. The manufacturing and molding of thickcross-sections, though timely, is completely dense, with no pores orvoids throughout the thick-walled parts.

Other suitable materials regularly accepted in the market place would beglass and mineral filled thermoplastic engineering resins, such as Nylon(PA), Poly-Phthal-Amide (PPA), Poly-Aryl-Ether-Ketone (PAEK),Poly-Ether-Ether-Ketone (PEEK), Poly-phenylene Sulfide (PPS), andPoly-Ketone (POK), or a mixture of the foregoing. Many of thesematerials are also offered without reinforcements, as the reinforcementshave potential to be abrasive to the steel tubing. Thermoplasticmaterials are, however, melt-processable, are designed to soften and dosoften when heated, and therefore lose strength, mechanical stability,and modulus, which are significant drivers for wear resistant materials.Because of this, the product life of thermoplastic materials in elevatedtemperature environments is limited. The molding process described indetail herein can be adapted for the injection of thermoplastic resins.

Other designed-in benefits with the helical design allow for 360-degreeprotection around the rod without inhibiting fluid flow. Based on marketresponse and experience, the grade of production tubing (hardness of thesteel) and the rod guide material used in centralizer application(abrasive fillers) may create wear tracks in the tubing. Some of thesecan also come from erosion or corrosion and fluid flow patterns aroundthe guide profile and through the movement of the rod string within thetubing. 360-degree protection inhibits the concern of wear tracks fromindividual vanes within the tubing. Currently the market prefers the useof sucker rod rotators which slowly rotate the rod string as the surfacepumping unit moves up and down. This is an acceptable practice todistribute wear evenly across the standard 4-vane sucker rod guidedesign. Wear rates are dependent on compressive loading between theplastic profile and the sucker rod and production tubing (side-load, asindustry defines it through sucker rod string design programs) andin-turn, the surface area taking that compressive loading. An increasein bearing surface area (denominator) in contact with the tubing reducesthis compressive pressure, reducing material wear rates. Because of thisphenomenon, rod guide centralizer manufacturers with larger surface areavanes made from inferior thermoplastic materials may wear at anacceptable rate in comparison to a preferred thermoset phenolic materialwith vane of that which is less surface area. This creates a ratio ofsurface area to material properties which can be extrapolated andcompared to various products theoretical wear life. Actual compressivestress on the sucker rod centralizer or stabilization tool vane dividedby the Compressive Strength can provide a relative parameter from oneproduct and material centralizer design to another. This would thenassist in extrapolating theoretical product performance. Thermoplasticmaterials have a drastic loss of mechanical strength and integrity atelevated temperatures (FIG. 14); however, thermosets such as phenolic,do not realize this same loss in performance. A lower value forStress-Strength Analysis allows for greater confidence in probabilityand reliability of the part in application. Operators desire the longestlasting sucker rod protection devices possible at an economical priceand with stable, predictable performance.

${{{{Compressive}{Strength}} = {{value}{from}{datasheet}}},{{relative}{to}{application}{temperature}}}{{{COMPRESSIVE}{STRESS}({PSI})} = \frac{{SIDE}{LOAD}{FORCE}({LBS})}{{BEARING}{SURFACE}{AREA}( {{SQ}.{IN}.} )}}$${{Stress} - {Strength}{Analysis}} = \frac{{Compressive}{Stress}({psi})}{{Compressive}{Stress}({psi})}$

In addition to the bearing surface calculation as a result of studyingthe vane width from various rod guide centralizers versus thestabilization tool herein, another engineered benefit of the helicalprofile includes a drastic increase in bearing surface as the productwears down. Typical centralizers do see some improvement of bearingsurface as the product wears, until its core diameter is found, and thenthe bearing surface area is substantially improved, although typicallybelow the product life minimum diameter. The helical design engages moreand more surface area as the product wears, allowing for a dynamicallyimproving bearing surface area which reduces compressive pressure,further elongating the product life. This is a feature unique to theenclosed invention. See graphic below showing before and after withcalculations related to the bearing surface area from one standard rodguide in comparison to the 360-degree helical sucker rod stabilizer.

FIGS. 24 and 25 are perspective views illustrating the high erodiblewear volume (“EWV”) of the stabilizer of the present disclosure, ascompared to the erodible wear volume of conventional prior artcentralizers. FIG. 24 corresponds to the EWV for Table A and FIG. 25corresponds to the EWV values listed in Table C below.

TABLE B More Contact Surface Area is Better for Wear Resistance SurfaceArea, Surface Area, Surface Area, 100% New 50% Worn 0% End-of-LifeProduct Product Product Helical   11 sq. in. 12.855 sq. in. 14.282 sq.in. Stabilizer Large 4.177 sq. in. 10.297 sq. in. 12.824 sq. in.Thermoplastic Market Offering Large Thermoset 3.091 sq. in.  7.711 sq.in.  9.936 sq. in. Market Offering

Manufactured in the preferred way with polymeric materials, thestabilization tool with inevitably experience wear against the steeltubing. This is by design as the stabilization tool shall not causedamage to the sucker rod or production tubing. The volume of materialthat can be worn away, in a traditional 4-fin centralizer design, iscommonly referred in industry to “Erodible Wear Volume”. That is, thevolume of plastic that may erode away before a metal sucker rod orcoupling can make contact to production tubing. The metric is skewed inindustry, as it does not take into account the rates at which polymericmaterial composition wears. Therefore, comparing dissimilar materials byan EWV factor only is a shortsighted view for trying to create acomparative example for marketing and sales purposes.

For our review and with our intention to use thermoset resins as thematerial makeup of the single fin, helical wrap stabilization tooldisclosed herein, EWV comparisons can be made between other thermosetphenolic centralizers to which the stabilization tool may findreplacing, due to enhanced feature set of additional protection on thesucker rod. The enhanced features include the primary driver for thedesign of the product, stabilizing the sucker rod in compressive momentsto prevent axial deflection and bending moments which result in rapidfatigue and failure of sucker rod.

TABLE C Product EWV (in³) ¾″ Sucker Rod Stabilization Tool 8.90 in³ ¾″Legacy Thermoset 5.35 in³ Centralizer

With more available EWV, the product has undoubtedly more wear life thanthat of a traditional 4-fin legacy thermoset sucker rod centralizer.Further, the material compositions are synonymous, and lastly, thebearing surface area discussed earlier further validates astress-reduction on the plastic, which lowers its stress:strength ratio,leading to another factor which establishes exponential increase inproduct life unique to this invention.

Operators have concern with an increase in friction loading due to moreplastic guides or surface area in contact with the inner surface of theproduction tubing; the load/force between the two materials does notchange. An increase of surface area directly and proportionally reducesthe pressure between the two surfaces, creating a negligible effect. Noadditional frictional loading will take place between abundant plasticto tubing contact and minimal plastic to tubing contact. The pound-forceloading between the two is the same.

μ=Coefficient of Friction between plastic and steel, lubricated

μ=varies between 0.06 and 0.14, according to industry studies

Drag Load (lbs)=(μ)(Side-Load Force, lbs)

Coefficient of friction and drag load are not driven whatsoever bysurface area touching the tubing. Instead, it is directly and onlyproportional to the side-load force and friction coefficient of thepolymeric materials. An increase in centralizer material does reduce thecompressive pressure (stress) on the materials therefore increasing itswear life. Ideally, product designers of centralizers would maximizesurface area in contact with production tubing for a reduction ofcompressive pressure between the sucker rod and tubing without reducingfluid flow paths which can create an increase in fluid drag.

Distributed surface area across the tubing allows for a significantreduction in compressive stress and pressure between the centralizationdevice and tubing, therefore furthering the life by reducing theerosion/wear of the centralizer material. If you consider a 50 lb. loadapplied on an abrasive sheet such as sandpaper, to a 12″×12″ floor andthe same load across a larger abrasive sheet on a 36″×36″ floor, theload doesn't change, only surface area did. The abrasive and reductionof pressure, however, is less effective at removing material, thereforewear life increases. With an increase in surface area, you have reducedthe pressure applied to the surface, which reduces the friction on a perunit basis, yet the frictional drag overall is the same.

The helical profile for the invention could be applied to the rod in onepiece or multiple sections. To be effective, the rod shall be reinforcedwith the helical pitch, whether in sections or with one singlecontinuous coil component, from end to end for the maximum effect andbenefit related to the prevention of sucker rod buckling within theproduction tubing.

A simple analysis was conducted to validate the benefit of the helicalprofile from end to end versus rod guides attached in commonconfigurations.

A summary table of the load values required to buckle the rod, assumingthe guides cannot move in the Y or Z direction due to the productiontubing constraint, is shown below:

TABLE D FEA Buckling Analysis, modes Design 1 2 3 4 Traditional 4 SuckerRod Guides 1,755 lbf 1,756 lbf 3,556 lbf 3,557 lbf Per Sucker Rod, EvenSpacing Traditional 8 Sucker Rod Guides 6,835 lbf 6,845 lbf 8,285 lbf8,287 lbf Per Sucker Rod, Double Up Spacing Traditional 8 Sucker RodGuides 7,412 lbf 7,422 lbf 20,060 lbf 20,078 lbf Per Sucker Rod, EvenSpacing 4 Component Helical Coil Stabilizers 10,370 lbf 10,380 lbf10,485 lbf 10,478 lbf Per Sucker Rod, Even Spacing 7 Component HelicalCoil Stabilizers 10,833 lbf 11,034 lbf 130,929 lbf 134,068 lbf PerSucker Rod, Even Spacing

Regarding the design of the helical profile as having one vane insteadof four vanes, this is done to maximize fluid flow bypass area acrossthe helical profile and sucker rod body during the downward motion ofthe sucker rod string within the production tubing. Furthermore, thereduction to one-vane from four-vanes vastly changes the area moment ofinertia (geometrical stiffness) of the stabilization tool. Often inapplication there is excessive stress created by sucker rod centralizerswhen sucker rods are put into compression. This occurs at the edges ofthe rod guides, bending moments, which lead to pre-mature sucker rodfailure. Reducing the cross section of the molded profile and extendingthe length of the sucker rod protection devices is preferred. A simplecomparison can be made with common lumber. A four-vane traditionalsucker rod centralizer comes in a variety of materials; however,geometrically one could metaphorically compare it to a 4×4 wood post.This wood post, compared to the invention disclosed herein, is much morestiff than comparatively speaking a 2×2 post. Because the reduction ofcross-sectional area is down by nearly 75%, the profile, although thesame material, is much more flexible. This design approach is unheard ofin the world of sucker rod centralizers or protection devices. Thecoiled profile with its reduction in AMOI, with the higher modulusphenolic reinforced material, is nearly 2× more flexible than the suckerrod itself, and up to seven times more flexible than traditional suckerrod guide/centralizer profiles of the same material. In order to createa traditional sucker rod guide profile with the same flexibility as theinvention herein, the modulus E must be reduced by 7×. With polymermaterial science properties available, this would result in a materialthat is too soft to be wear resistant for suitable use in application.Of course, the operators and users of the sucker rod centralizers orstabilization products want the investment they made to last as long aspossible without providing negative effects to the sucker rod for someauxiliary reason (too stiff). The material science and options ofpolymers for downhole use has plateaued due to technologies availabletoday both on the thermoset and thermoplastic side of the market. Thefuture of sucker rod protection lies with creative geometry as disclosedherein.

For instance:

E=modulus of elasticity

I=area moment of inertia

Stiffness Matrix=(E)(I)

Common wear resistant sucker rod guide (XX direction):

E=2,400,000 psi

I=0.775 in⁴

Stiffness Matrix=(E)(I)=(2,400,000)(0.775)=1,860,000

¾″ Sucker rod:

E=29,700,000 psi

I=0.0155 in⁴

Stiffness Matrix-(E)(I)=(29,700.000)(0.0155)=461,287

Stabilization Tool disclosed herein:

E=2.400.000 psi

I=0.11 in⁴

Stiffness Matrix=(E)(I)=(2,400,000)(0.11)=264,000

Combining the stiffness of the geometry and the material modulus showsthat the helical coil profile is nearly 2× more flexible in the XXdirection evaluated, in comparison to the steel ¾″ sucker rod.

To match the stiffness of the ¾″ sucker rod yet provide the longestlasting, stable down-hole thermoset material, the maximum AMOI may becalculated:

E_(steel) = 29, 700, 000psiE_(plastic) = 2, 400, 000psiI = 0.0155in⁴${{Stiffness}{Matrix}{Comparison}( E_{steel} )( I_{steel} )} = {{( E_{plastic} )( I_{plastic} )\frac{( E_{steel} )( I_{steel} )}{( E_{plastic} )}} = {{( I_{plastic} )\frac{( {29,700,000} )(0.0155)}{( {2,400,000} )}} = {0.191 = ( I_{plastic} )}}}$

The AMOI range of common sucker rod guides varies but for typical 4-vanevariants, is between 0.600 in⁴-0.800 in⁴.

FIG. 26 illustrates a process for engineering a stabilizer according tothe present disclosure, including inhibiting sucker rod buckling duringcompression moments in artificial lift wells. The various steps shown inFIG. 26 are followed as illustrated, and taking into account variousdesign factors, including the following:

Design Factors for Polymeric Product Life:

-   -   Erodible Wear Volume    -   Bearing Surface Area    -   Material selection (material science, plastics are non-linear,        thermosets are nearly linear) Ideal Factors Industry Use:    -   Impact Strength    -   Fluid Flow Bypass Area (cross-sectional area around the guide        and sucker rod and inside of the production tubing    -   Fluid Turbulence—1-fin vs 4-fin allows for drastic increase in        fluid bypass area    -   High EWV, Long lasting plastic in all temperatures    -   Buckling inhibition    -   Constant sucker rod reinforcement    -   No stress/bending moment at edge of rod guide Manufacturing        requirements:    -   Throughput, consistent manufacturing, quality    -   Traceability    -   Care and handling of customer sucker rod New and Useful        Benefits:    -   Geometric flexibility+long lasting plastic=longest and strongest        sucker rod protection ever created    -   Unique design of plastic allows for minimal increase in material        yet major increase in EWV, fluid flow area, and product        flexibility Information/variables to be addressed or known to        effectively design:    -   Calculate maximum spacing for stabilization tools:    -   Max compressive load (weight of rod string above rod in        question)    -   Sucker rod material (modulus of elasticity)    -   Sucker Rod diameter (AMOI calculation)    -   Manufacturability    -   Material science and associated equipment for quality parts    -   Material science for polymer performance in well (Tg analysis)    -   Tooling design creativity for part release or variable lengths.    -   Cost of resin and associated labor costs    -   Product Analysis    -   EWV metrics from other market offerings    -   Stiffness matrix of other market offerings (modulus*AMOI)    -   Fluid Flow characteristics of other products    -   FEA of molded part with sucker rod.

Thus, the advantages of this invention provide a stabilizer forinhibiting sucker rod buckling during compression moments in artificiallift wells, reducing bending moments and stress, increasing thestability of sucker rods, increasing sucker rod fatigue life, and amodular tooling design as a method of manufacturing. The manufacturingmethod is also new and unique, providing extensive assurance and benefitto the end-users and operators as the quality and manufacturing systemis in place for machine regulated manufacturing, removing an abundantamount of human error and interpretation which often causes sub-par orunder-performing parts for the end-users and oilfield operators andproduction companies. The sucker rod is constantly reinforced throughthe engineered helical pitch to which the calculated critical bucklingload exceeds that which is attainable in the production well.Centralizing the sucker rod throughout the body consistently from end toend instead of periodically like traditional use of sucker rod guidesproves more effective and a healthier approach regarding down-holedynamics of sucker rod pumping systems. The coiled profile is proven tobe more flexible than the sucker rod due to the reduction in Area Momentof Inertia, not affecting the natural motion of the sucker rod due togeometrical stiffness. Instead, the sucker rod protection andanti-buckling behavior is created through the physical occupation ofspace between the sucker rod and the production tubing.

Although the preferred embodiment has been described in detail, itshould be understood that various changes, substitutions, andalterations can be made therein without departing from the spirit andscope of the invention as defined by the appended claims.

What is claimed is:
 1. A stabilizer and a sucker rod for use withinproduction tubing, said stabilizer and sucker rod comprising: a moldedsolid body formed of polymeric materials which defines said stabilizer;said molded solid body having a vane formed with a helically shapedprofile which continuously extends around a longitudinal axis of saidsucker rod, wherein said helically shaped profile of said vane angularlyextends fully around said sucker rod; said vane configured such thatsaid helically shaped profile of said vane has a pitch which extendswith a length disposed parallel to said longitudinal axis, with at leastone wrap of said vane extending fully around said sucker rod, and saidlength of said pitch configured such that an outer surface of said vaneengages said production tubing and prevents an adjacent section of saidsucker rod from contacting said production tubing; wherein a crosssection of said vane which extends transverse to said longitudinal axishas a radial length extending between said outer surface said vane andsaid exterior surface of said sucker rod, and a thickness which extendstransverse to said radial length; said molded solid body wherein aninterior surface of said vane is sized for closely fitting about anexterior of said sucker rod for retaining said vane in fixed positionrelative to said sucker rod.
 2. The stabilizer and the sucker rodaccording to claim 1, wherein said thickness of said vane issubstantially the same as the exterior diameter of said sucker rod. 3.The stabilizer and the sucker rod according to claim 1, wherein saidmolded solid body of said stabilizer is secured in fixed positionrelative to said sucker rod with an adhesive applied between saidexterior surface of said sucker rod and said interior surface of saidvane.
 4. The stabilizer and the sucker rod according to claim 1, whereininterior surfaces of said vane and said at least one collar are sizedfor closely fitting about an exterior of said sucker rod with aninterference fit which retains said vane and said at least one collar infixed position relative to said sucker rod.
 5. The stabilizer and thesucker rod according to claim 1, further comprising an upper moldedcollar and a lower molded collar disposed on opposite terminal ends ofsaid vane with said at least one collar disposed there-between, whereinsaid upper molded collar and said lower molded collar are sized forclosely fitting about said exterior of said sucker rod for retainingsaid vane in said fixed position relative to said sucker rod.
 6. Thestabilizer and the sucker rod according to claim 5, wherein interiorsurfaces of said vane, said at least one collar, said upper moldercollar, and said lower molded collar are sized for closely fitting aboutan exterior of said sucker rod with an interference fit which retainssaid vane and said at least one collar in fixed position relative tosaid sucker rod.
 7. The stabilizer and the sucker rod according to claim1, wherein said vane and said at least one collar are formed of a solidpolymeric material, over-molded onto said sucker rod, and an exteriorperiphery of said vane defines a wear surface for engaging an interiorwall of a production tubing.
 8. The stabilizer and the sucker rodaccording to claim 1, wherein said helical pitch is computed to allowfor constant reinforcement of the sucker rod, whereas reinforcement ofsucker rods in are string are provided by use of multiple stabilizers ina frequency which is greater than the buckling tendency and capabilityof said sucker rod in a particular rod-pumping application.
 9. Thestabilizer and the sucker rod according to claim 1, wherein said atleast one collar wraps fully and continuously around said sucker rod,and said vane has a cross-section which is substantially rectangular inshape, with arcuately shaped inward and outward ends.
 10. The stabilizerand the sucker rod according to claim 1, further comprising at least onecollar which is centrally disposed adjacent to and continuous with saidvane, and wherein said at least one collar is shaped to wrap fullyaround said sucker rod with a shrink fit engagement, and said at leastone collar having a cylindrical shape.
 11. A stabilizer and a sucker rodfor use within production tubing, said stabilizer and sucker rodcomprising: a molded solid body formed of polymeric materials whichdefines said stabilizer; said molded solid body having a vane formedwith a helically shaped profile which continuously extends around alongitudinal axis of said vane, wherein said helically shaped profile ofsaid vane angularly extends fully around said sucker rod, with saidlongitudinal axis of said vane disposed coaxial with a sucker rodlongitudinal axis; said vane configured such that said helically shapedprofile of said vane has a pitch which extends with a length disposedparallel to said longitudinal axis, with at least one wrap of said vaneextending fully around said sucker rod, and said length of said pitchconfigured such that an outer surface of said vane engages saidproduction tubing and prevents an adjacent section of said sucker rodfrom contacting said production tubing; wherein a cross section of saidvane which is disposed perpendicular to said longitudinal axis has aradial length extending between said outer surface said vane and saidexterior surface of said sucker rod, and a thickness which extendsperpendicular to said radial length; and said molded solid body furtherincluding at least one collar disposed in continuous relation to saidvane, wherein interior surfaces of said vane and said at least onecollar are sized for closely fitting about an exterior of said suckerrod for retaining said vane and said at least one collar in fixedposition relative to said sucker rod.
 12. The stabilizer and the suckerrod according to claim 11, wherein said molded solid body of saidstabilizer is secured in fixed position relative to said sucker rod withan adhesive applied between said exterior surface of said sucker rod andsaid interior surface of said vane and said at least one collar.
 13. Thestabilizer and sucker rod according to claim 11, wherein interiorsurfaces of said vane and said at least one collar are sized for closelyfitting about an exterior of said sucker rod with an interference fitwhich retains said vane and said at least one collar in fixed positionrelative to said sucker rod, and said at least one collar wraps fullyand continuously around said sucker rod.
 14. The stabilizer and suckerrod according to claim 11, further comprising an upper molded collar anda lower molded collar disposed on opposite terminal ends of said vanewith said at least one collar disposed there-between, wherein said uppermolded collar and said lower molded collar are sized for closely fittingabout said exterior of said sucker rod for retaining said vane in saidfixed position relative to said sucker rod.
 15. The stabilizer andsucker rod according to claim 14, wherein interior surfaces of saidvane, said at least one collar, said upper molder collar, and said lowermolded collar are formed of a solid polymeric material which isover-molded onto said sucker rod, and sized for closely fitting about anexterior of said sucker rod with an interference fit which retains saidvane and said at least one collar in said fixed position relative tosaid sucker rod, and an exterior periphery of said vane defines a wearsurface for engaging an interior wall of a production tubing.
 16. Thestabilizer for a sucker rod according to claim 11, wherein said helicalpitch is computed to allow for constant reinforcement of the sucker rod,whereas reinforcement of sucker rods in are string are provided by useof multiple stabilizers in a frequency which is greater than thebuckling tendency and capability of said sucker rod in a particularrod-pumping application.
 17. The stabilizer for a sucker rod accordingto claim 11, further comprising said vane having a cross-section whichis substantially rectangular in shape, with arcuately shaped inward andoutward end, and said thickness of said vane is substantially the sameas the exterior diameter of said sucker rod.
 18. A stabilizer and asucker rod for use within production tubing, said stabilizer and suckerrod comprising: a molded solid body formed of polymeric materials whichis over-molded onto said sucker rod to define said stabilizer, saidmolded solid body having a vane formed with a helically shaped profilewhich continuously extends around a longitudinal axis of said vane,wherein said helically shaped profile of said vane angularly extendsfully around said sucker rod, with said longitudinal axis of said vanedisposed coaxial with a sucker rod longitudinal axis; said vaneconfigured such that said helically shaped profile of said vane has apitch which extends with a length disposed parallel to said longitudinalaxis, with at least one wrap of said vane extending fully around saidsucker rod, and said length of said pitch configured such that an outersurface of said vane engages said production tubing and prevents anadjacent section of said sucker rod from contacting said productiontubing; wherein a cross section of said vane which is disposedperpendicular to said longitudinal axis has a radial length extendingbetween said outer surface said vane and said exterior surface of saidsucker rod, and a thickness which extends perpendicular to said radiallength; said molded solid body further including an upper molded collarand a lower molded collar disposed on opposite terminal ends of saidvane, and an intermediate collar disposed there-between, wherein saidupper molded collar, said lower molded collar, and said intermediatecollar are disposed in continuous relation to said vane, and haveinterior surfaces which sized for closely fitting about said exterior ofsaid sucker rod for retaining said vane in said fixed position relativeto said sucker rod; and wherein said molded solid body is are formed ofa solid polymeric material, over-molded onto said sucker rod to providesaid upper molded collar, said lower molded collar, said intermediatecollar and said vane, with an exterior periphery of said vane providinga wear surface for engaging an interior wall of a production tubing. 19.The stabilizer and the sucker rod according to claim 18, wherein saidmolded solid body of said stabilizer is secured in fixed positionrelative to said sucker rod with an adhesive applied between saidexterior surface of said sucker rod and said interior surface of saidvane and said at least one collar.
 20. The stabilizer and sucker rodaccording to claim 18, wherein interior surfaces of said vane and saidat least one collar are sized for closely fitting about an exterior ofsaid sucker rod with an interference fit which retains said vane andsaid at least one collar in fixed position relative to said sucker rod,and said at least one collar wraps fully and continuously around saidsucker rod.